Efeito da adição de glutationa na função e estresse oxidativo em sêmen ovino criopreservado Effect of glutathione on the function and oxidative status of ovine cryopreserved sperm

The high susceptibility of sperm to the oxidative stress occurs especially due to high content of poly-unsaturated fatty acids (PUFAs) in its plasma membrane. The PUFAs provide the necessary fluidity to the plasma membrane. However double bonds present in those fatty acids are more susceptible to oxidative stress. Studies in human indicate that cryopreservation may lead to damages to the sperm due to oxidative stress. This study aimed to verify if the antioxidant glutathione (GSH) may protect ovine cryopreserved sperm against damages caused by oxidative stress. Semen samples of four rams were cryopreserved using Tris-egg yolk extender supplemented with different concentrations of reduced glutathione (control, 1, 5 and 10 mM). After thawing, samples were evaluated using conventional (motility and vigor) and functional tests (membrane integrity and mitochondrial activity). Aliquots of each thawed sample were submitted to protocol of induced lipid peroxidation using ascorbate (20 mM) and ferrous sulphate (4 mM), with further measurement of tiobarbituric acid reactive substances (TBARS), index of oxidative stress. No effect of GSH was observed on variables assessed by conventional tests. GSH decreased the proportion of intact acrosomes. Samples treated with 5 mM GSH showed lower percentage of intact membrane cells when compared to control samples and those treated with 10 mM. The percentage of cells with mitochondrial activity was affected by GSH, but no effect on TBARS. Samples from control group were more susceptible to denaturation of chromatin. In conclusion, the addition of Glutathione (GSH) offers protection to DNA and mitochondrial activity of ovine sperm.